Chlorine-containing resins such as vinyl chloride resins have excellent flame retardancy and chemical resistance; therefore, they are used in a variety of applications. However, chlorine-containing resins have a drawback in that they are thermally degraded to cause dehydrochlorination which leads to a reduction in the mechanical strength and occurrence of coloration as well as deterioration of the marketability.
In order to solve the above-described drawback, a variety of stabilizers have been developed and, in particular, for example, a mixture of a lead or cadmium compound and a barium compound is known to have superior stabilizing effect. However, in recent years, from the safety standpoint, the trend is toward restricting the use of lead compounds and cadmium compounds, so that stabilization by a lead or cadmium compound is now being replaced by stabilization provided by combinatory use of a highly safe zinc compound and an organic acid salt of alkaline earth metal or an inorganic compound such as hydrotalcite or zeolite. For example, in Patent Document 1, it is disclosed that magnesium hydroxide and a zinc hydrotalcite compound are combined to provide a rigid to semi-rigid chlorine-containing polymer in which foaming during processings is suppressed.
Yet, since such low toxic stabilizers alone cannot provide sufficient stabilizing effect, in order to improve the resistance to light, heat, oxidation and the like, a variety of additives such as organic phosphite compounds, epoxy compounds, phenolic antioxidants, benzophenone-based or benzotriazole-based ultraviolet absorbers and hindered amine-based light stabilizers are also used in combination.